Tire tread for a heavy vehicle with improved robustness

Abstract

A tire tread ( 1 ), for a heavy-duty construction plant vehicle, having an improved compromise between resistance to mechanical attack caused by stony ground and grip on muddy ground. The tread ( 1 ) has five rows ( 41, 42, 43 ) separated in pairs by a longitudinal cut ( 51, 52 ) and are distributed, along the transverse direction (YY′), in a median row ( 43 ), two intermediate rows ( 42 ), and two lateral rows ( 41 ), the blocks ( 31, 32, 33 ) in one and the same row ( 41, 42, 43 ) separated in pairs at least partially by a transverse cut ( 61, 62, 63 ), each transverse cut in a lateral row ( 41 ) is a transverse groove, each transverse cut ( 62 ) in an intermediate row ( 42 ) is either a blind transverse groove ( 621 ), or a transverse sipe ( 622 ), are arranged in alternation along the longitudinal direction XX′, and each inner longitudinal cut ( 52 ) separating two adjacent rows ( 42, 43 ), respectively intermediate and median, is a longitudinal groove.

The invention claimed is: 
     
         1 . A tread of a tire for a heavy-duty vehicle that is intended to come into contact with the ground via a tread surface, comprising blocks which are arranged in rows along a longitudinal direction (XX′) and are delimited by cuts,
 the tread having a width (L), measured along a transverse direction (YY′) between two lateral edges of the tread surface, and a height (H), which is equal to the maximum depth of a cut measured along a direction perpendicular to the tread surface, 
 wherein the cuts are;
 inner longitudinal grooves having a depth (PR) at least equal to 50% of the height (H) of the tread and a width (WR) at least equal to 20% of the said depth (PR), and 
 outer longitudinal sipes having a depth (PI) at least equal to 50% of the height (H) of the tread and a width (WI) strictly less than 20% of the said depth (PI), 
 
 the tread comprising five rows which are separated in pairs by the inner longitudinal grooves and outer longitudinal sipes and are distributed, along the transverse direction (YY′), in a median row, centred on a median plane (XZ) perpendicular to the tread surface at its middle, two intermediate rows, which are on either side of the median row and are symmetrical in relation to the median plane (XZ), and two lateral rows, which are transversely outermost and symmetrical in relation to the median plane (XZ), 
 the blocks in each respective row being separated in pairs at least partially by a transverse cut, 
 wherein each transverse cut in a lateral row is a transverse groove extending from a lateral edge of the tread surface to a respective outer longitudinal sipe, 
 wherein each transverse cut in an intermediate row is either:
 a blind transverse groove, which continues a transverse groove in the neighbouring lateral row and extends from the respective outer longitudinal sipe to a transversely inner end (E 2 ) of the blind transverse groove, or 
 a transverse sipe extending from the respective outer longitudinal sipe to a respective inner longitudinal groove, 
 wherein every blind transverse groove alternates with a transverse sipe, along the longitudinal direction (XX′), and 
 
 wherein each inner longitudinal cut separating two adjacent rows, respectively intermediate and median, is a are the inner longitudinal grooves. 
 
     
     
         2 . The tread according to  claim 1 , wherein each outer longitudinal sipe has a mean line (M 1 ) positioned, in relation to the median plane (XZ) of the tread and along the transverse direction (YY′), at a mean distance (D 1 ) at least equal to 20% of the width (L) of the tread. 
     
     
         3 . The tread according to  claim 1 , wherein each outer longitudinal sipe has a mean line (M 1 ) positioned, in relation to the median plane (XZ) of the tread and along the transverse direction (YY′), at a mean distance (D 1 ) at most equal to 35% of the width (L) of the tread. 
     
     
         4 . The tread according to  claim 1 , wherein each transversely inner end (E 2 ) of a blind transverse groove in an intermediate row is positioned, in relation to the median plane (XZ) of the tread and along the transverse direction (YY′), at a distance (D 2 ) at least equal to 20% of the width (L) of the tread. 
     
     
         5 . The tread according to  claim 1 , wherein each transversely inner end (E 2 ) of a blind transverse groove in an intermediate row is positioned, in relation to the median plane (XZ) of the tread and along the transverse direction (YY′), at a distance (D 2 ) at most equal to 35% of the width (L) of the tread. 
     
     
         6 . The tread according to  claim 1 , wherein each inner longitudinal cut has a mean line (M 3 ) positioned, in relation to the median plane (XZ) of the tread and along the transverse direction (YY′), at a mean distance (D 3 ) at least equal to 5% of the width (L) of the tread. 
     
     
         7 . The tread according to  claim 1 , wherein each inner longitudinal groove has a mean line (M 3 ) positioned, in relation to the median plane (XZ) of the tread and along the transverse direction (YY′), at a mean distance (D 3 ) at most equal to 20% of the width (L) of the tread. 
     
     
         8 . The tread according to  claim 1 , wherein each transverse cut in the median row is a transverse sipe which continues a transverse sipe in the neighbouring intermediate row and extends from a first inner longitudinal cut to a second inner longitudinal cut. 
     
     
         9 . The tread according to  claim 1 , wherein each block in a lateral row that are delimited by two consecutive transverse grooves, having a block height (H 1 ) along a direction perpendicular to the tread surface (ZZ′) and a block length (B 1 ) along the longitudinal direction (XX′), wherein the block height (H 1 ) is at most equal to 80% of the block length (B 1 ). 
     
     
         10 . The tread according to  claim 1 , with each block in a lateral row having a block length (B 1 ) along the longitudinal direction (XX′), and each transverse groove, delimited by two blocks, having a transverse groove width (W 1 ) along the longitudinal direction (XX′), wherein the transverse groove width (W 1 ) is at least equal to 18% of the sum of the transverse groove width (W 1 ) and the block length (B 1 ). 
     
     
         11 . The tread according to  claim 1 , with each block in a lateral row having a block length (B 1 ) along the longitudinal direction (XX′), and each transverse groove, delimited by two blocks, having a transverse groove width (W 1 ) along the longitudinal direction (XX′), wherein the transverse groove width (W 1 ) is at most equal to 35% of the sum of the transverse groove width (W 1 ) and the block length (B 1 ). 
     
     
         12 . The tread according to  claim 1 , wherein at least one ventilation cavity, opening into the tread surface and having a depth (PC) at least equal to 70% of the height (H), is positioned, along the longitudinal direction (XX′), between at least two consecutive transverse grooves in one and the same lateral row. 
     
     
         13 . The tread according to  claim 1 , with the tread comprising two outer lateral faces, each intersecting the tread surface at a lateral edge of the tread surface, all transverse grooves in a lateral row opening into a lateral face of the tread along an open section, wherein at least one ventilation cavity, opening into a lateral face of the tread but not onto the tread surface when the tire is new, is positioned, along the longitudinal direction (XX′), between at least two surfaces into which consecutive transverse grooves in one and the same lateral row open. 
     
     
         14 . A tire for a heavy-duty vehicle, that comprises a tread according to  claim 1 .